MEGACOLON.pptx

MEGACOLON

1. MEGACOLON

2. Megacolon is of two types ( 1) Congenital megacolon or primary megacolon ( Hirschsprung’s disease. ( 2) Secondary or acquired megacolon .

3. PRIMARY MEGACOLON (HIRSCHSPRUNG’S DISEASE) Massive dilatation and hypertrophy of the colon in children

4. Aetiology and Pathogenesis It is caused by absence of ganglionic cells of the pelvic parasympathetic system in both Auerbach’s plexus between the circular and longitudinal muscle layers of the colon and Meissner's plexus in the submucosa . It is believed to be the result of failure of migration of neuroblasts into the gut from nerve trunks. It usually occurs at the end of the first trimestar of foetal life.

5. Aetiology and Pathogenesis Aganglionosis may result if there cessation of migration of neuroblasts , which migrate from the primitive node along the alimentary track distalwise . The internal anal sphincter is aganglionic in every case of Hirschsprung’s disease. This aganglionosis extends proximaliy to variable distance according to the failure of descent of the neuroblasts .

6. Aetiology and Pathogenesis Approximately 80% of cases involve the rectosigmoid junction and 15% have aganglionic segment extending as far proximaliy as the hepatic flexure . The former condition is called ‘short segment aganglionosis ’ and the latter condition is called ‘long segment aganglionosis ’. There are some cases where aganglionosis occurs in skip areas, these are known as ‘ segmental aganglionosis ’.

7. Aetiology and Pathogenesis There is absence of peristalsis in the aganglionic segments thus producing adynamic intestinal obstruction . Lack of peristalsis in the aganglionic segment and failure of relaxation of the internal anal sphincter produce varying degrees of intestinal obstruction found in this disease.

8. PATHOLOGY The bowel proximal to the aganglionic segment becomes gradually dilated and hypertrophied for a variable length as the peristaltic waves try to propel stools through the obstructing aganglionic segment

9. PATHOLOGY There is a visible transition zone, usually 1 to 5 cm in length between the dilated bowel which contains ganglionic cells on the proximal side and normal sized aganglionic segment of bowel on the distal side. All layers of the dilated intestine show gross pathological changes. The mucous lining is chronically inflamed and frequently ulcerated.

10. PATHOLOGY The pelvic mesocolon is elongated and thickened and its blood vessels are large and prominent . As in majority of cases the aganglionic segment stops proximaliy at sigmoid colon, the grossly dilated portion mostly involves the upper sigmoid colon and lower descending colon.

11. Clinical features This condition is more common in males and it shows familial tendency. The symptoms appear within 3 days of birth and the presenting features are as follows : ( i ) Constipation ( ii) Abdominal distension

12. Clinical features ( i ) Constipation The new born child fails to pass meconium within first 2 or 3 days. If the little finger is introduced into the rectum meconium is passed in inadequate amount and toothpaste like.

13. Clinical features (ii) Abdominal distension This becomes obvious by the 3rd day. Gradually the distension progresses and the colon is involved in distension. Visible peristalsis may be seen with loud borborygmi .

14. Clinical features In some babies the symptoms may suggest mild gastroenteritis or a feeding problem associated with mild constipation . As the condition becomes more chronic the baby fails to gain weight, becomes hypoproteinaemic and suffers from intermittent episodes of severe constipation and diarrhoea.

15. Clinical features Eventually enterocolitis may develop , a lethal complication of Hirschsprung’s disease. The clinical picture includes fever, vomiting, watery or bloody diarrhoea, septic shock and finally death. Enterocolitis develops due to invasion of bacteria from the dilated colon through erosion and ulceration in the mucosa into the wall of the colon. Immediate vigorous management is indicated

16. Rectal examination Reveals that the rectum is empty and the anus is free from any pathology.

17. Special Investigations 1 . BARIUM ENEMA EXAMINATION This should be done in unprepared bowel as wash-outs may minimise the dilatation of the gut above the obstruction. Barium enema should be prepared with normal saline and not with water, as magacolon absorbs water much more rapidly than normal bowel and may result in water intoxication.

18. MEGA COLON

19. This examination will demonstrate dilated colon followed by narrow aganglionic segment. The diagnosis becomes difficult if the child has a very short segment involved or if the entire colon is aganglionic . In infants the proximal non-affected colon may not become very much dilated , but in these cases the retention of barium after 24 hours is quite diagnostic. It is always essential that both anteroposterior and lateral views should be taken as narrow short segments may be overlapped by dilated proximal colon in one of the views.

20. HIRSCHSPRUNG’S DISEASE

21. 2. RECTAL BIOPSY W ill demonstrate absence of ganglionic cells in the intramural and submucous plexuses . Biopsy should be taken at least 2 cm above the dentate line. An attempt should be made to take full thickness wall for biopsy, as superficial biopsy cannot confirm presence or absence of ganglion cells in the intramural plexus.

22. 3. MANOMETRIC STUDIES Can be done easily in the older children and absence of relaxation of the internal anal sphincter will confirm the diagnosis.

23. Treatment The main curative treatment of this disease is excision of the entire aganglionic segment (the cause of functional obstruction) and continuity is restored with normal sphincteric control of the anus. COLOSTOMY